1. Field of the Invention
The present invention generally relates to plasma display apparatuses, and more specifically, the present invention relates to a plasma display apparatus in which the efficiency of emission of light is improved.
2. Description of the Related Art
FIG. 1 is an exploded perspective view showing the construction of an AC plasma display panel (hereinafter abbreviated as PDP) disclosed in U.S. Pat. No. 5,640,068. Referring to FIG. 1, the PDP includes a plurality of display electrodes, only one of which is shown and is indicated by the reference numeral 141. The display electrode 141 extends in the row direction of the PDP. The display electrode 141 is constituted of a pair of electrodes X and Y having edges opposing each other. The display electrode 141 is formed on a front substrate 11, and is covered by a dielectric layer 17. The surface of the dielectric layer 17 is covered by a protective MgO film. The PDP also includes linear-shaped barrier ribs 129 extending in the column direction of the PDP. The height of the barrier ribs is usually on the order of 100 to 150 μm. The inner faces of the bulkheads 129 are coated with a phosphor member 28. The PDP further includes a plurality of address electrodes 22 to perform address discharge on the X electrode of the display electrode 141. The barrier ribs 129 and the address electrodes 22 are formed on a back substrate 21. Within the PDP, mixture of ionizable gases, such as xenon, neon, and helium, is sealed. The mixed gas is used to cause discharge and thereby generating ultraviolet rays, which excite the phosphor member 28 to cause emission.
In operation, first, a voltage higher than the breakdown voltage is applied between the X electrode of the display electrode 141 and the address electrodes 22 to cause an address discharge. At this time, a temporary discharge occurs between the electrodes X and Y, generating a charge on the surfaces of the electrodes X and Y. The charges generated on the surfaces of the electrodes X and Y due to the address discharge is referred to as a wall charge. After the address discharge, a pulse voltage lower than the breakdown voltage is applied between the electrodes X and Y of the display electrode 141; then, a discharge occurs between the electrodes X and Y of the display electrode 141 due to the wall charge generated by the address discharge. The discharge between the electrodes X and Y is called a sustaining discharge, which occurs only in the region where a wall charge is generated due to the address discharge. The sustaining discharge emits ultraviolet rays that excite the phosphor member 28 to cause luminescence.
FIG. 2 is an exploded perspective view showing the configuration of a PDP disclosed in U.S. Pat. No. 5,825,128. The PDP shown in FIG. 2 has meandering barrier ribs 129. Separation of discharge areas by the meandering barrier ribs 129 serves to enhance resolution of the PDP. Each of the areas separated by the barrier ribs 129 is generally called a cell.
The conventional PDPs with the constructions shown in FIGS. 1 and 2 have the following problems.
FIGS. 3A and 3B are schematic diagrams illustrating a state of discharge caused by the display electrodes 141 of the conventional PDPs shown in FIGS. 1 and 2. The problems of the conventional PDPs will be described with reference to FIGS. 3A and 3B. As shown in FIGS. 3A and 3B, a discharge produced in a gap (g) between the X and Y electrodes spreads in a direction away from the discharge gap (g), maintaining a circular or an elliptical shape, and terminates by reaching an inner surface of the barrier ribs 129. The energy of the discharge terminated by the inner surface of the barrier ribs 129 is dissipated as thermal energy without generating ultraviolet rays that excite the phosphor 28 to cause luminescence. The conventional PDP shown in FIG. 2, has the display electrode 141 formed continuously over multiple cells arranged in the row direction; thus, discharge spreads beyond a range of a single cell, as shown in FIG. 3A. This means the discharge is terminated by the inner surfaces of the barrier ribs 129 without causing the phosphor 28 to emit light.
On the other hand, the conventional PDP shown in FIG. 1, has continuous cells in the column direction; thus, discharge spreads beyond a range of single cell, as shown in FIG. 3B. This means the propagation loss of the ultraviolet rays emitted by discharge becomes greater as the energy propagates away from the discharge gap g in the column direction until reaching the surface of the phosphor 28. This is more prominent at the anode side, at which progression of discharge is smaller.
PDPs generate ultraviolet rays by discharging, and excite the phosphor 28 by the ultraviolet rays to cause emission of light. Therefor, the energy loss caused in that two processes must be minimized to produce luminescence efficiently.
The conventional PDPs have another problem caused by an electric field formed around the address electrode 22 disposed in the center of the cells, and this electric field disturbs the sustaining discharge generated by display electrode 141. The below further describes this problem. Because the address electrode 22 is composed of a conductive material such as metal, an intense electric field is formed around the address electrode 22 due to the electric field formed between the X and Y electrodes during a sustaining discharge. By way of example, if the pulse voltage for sustaining discharge is 180 V, the address electrode 22 is at a voltage between 180 V and 0 V, for example, 65 V, in which case voltage differences of 115 V and 65 V occurs between the address electrode 22 and the X and Y electrodes of the display electrodes 141, respectively, forming an intense electric field. FIG. 4A shows a distribution of electric field where the address electrode 22 is not disposed, and FIG. 4B shows a distribution of electric field where a voltage of 65 V is generated on the address electrode 22. FIG. 5A shows a discharge area corresponding to the distribution of electric field shown in FIG. 4A, in which the discharge is concentrated within the discharge gap g. FIG. 5B shows a discharge area corresponding to the distribution of electric field shown in FIG. 4B, in which the discharge extends over a large area, causing loss of discharge energy at the barrier ribs 129.
In PDPs, loss of discharge energy is a significant factor for power consumption. In the conventional PDPs, the display electrode 141, the barrier ribs 129, and the address electrode 22 are not configured so that the phosphor 28 emits light efficiently, resulting in necessity of high power supply.
It is therefor, a primary object of the invention to provide a plasma display apparatus that is able to emit high light with low energy supply.